I can only speak to the LEE dies because nearly every die set I have are LEE dies.  That said... the LEE dies are absolutely excellent, and their customer service (should you have a problem) is second to none!  (The only problem I ever had was with a stuck 30-06 case, and I bent the mandrel trying to pound the case out.  LEE sent me a new die and spare mandrel - no questions asked!!!)  LEE will cost you the least - something of importance to me since I ain't JP Morgan!

You'll hear people touting their brand as the end-all/be-all (especially Dillon products, which by the way will cost you a second mortgage), but the only advice I can give is go with your gut... they're all pretty good.